Do not encrypt the paper wallet so the Bitcoins are not lost when you lose the passphrase after so long time.
Forgetting/losing a password is going to be an issue no matter what method you chose, Paper or Trezor or Desktop wallet, etc. So you feel better security is to lock up the paper wallet rather than encrypting it eh?
All you need is to hide the paper wallet well, then the risk of physical theft is very small. The advantage is you dont need to remember any passphrase (you would need to store the passphrase somewhere as well). I using paper wallets and I think much bigger security concern for Bitcoin is computer malware, so I feel well hidden paper wallets with visible (unencrypted) private key is no security concern at all - it is like buying trezor, writting the 24 words to the paper sheet as is recommended and hide it well to have backup, these 24 words on the paper sheet are unencrypted as well and are equivalent of visible paper wallet private key.